Tank ship bulkhead and girder construction



April 10, 1956 v. ALBIACH 2,741,208

TANK SHIP BULKHEAD AND GIRDER CONSTRUCTION Filed Aug. 24, 1951 2Sheets-Sheet 1 INVENTOR. VINCENT ALBIACH April 0, 1956 v. ALBIACH TANKSHIP BULKHEAD AND GIRDER CONSTRUCTION 2 Sheets-Sheet 2 Filed Aug. 24,

INVENTOR. VINCENT HLsmcH HIS HTTOR EYS Unite rates Patent TANK mBULKHEAD AND GERBER CGNSTRUCTION Vincent Albiach, Paris, FranceApplication August 24, 1951, Serial No. 243,463

4 Claims. (Cl. 114-79) The instant invention relates to shipconstruction, and particularly to an improved tanker.

Among all the types of merchant ships, those vessels intended for thetransportation of petroleum or other liquids in bulk are particularlyaffected by conditions at sea. The reasons for placing the oil tanker inthis particular category are threefold.

In the first place, tankers are generally designed to navigate at theminimum freeboard permitted by the International Convention Tables onLoad Lines. To this end the superstructure is reduced to a minimum, andtherefore its contribution to the strength of the hull structure iscorrespondingly reduced. Secondly, the propelling installation isgenerally arranged aft, and seldom amidship' as is the case for themajority of other types of ships. This results in an increase of theloading of a tanker in the order of by comparison with a cargo ship ofthe same hullform but with the engines amidship. Finally, the nature ofthe cargo creates special problems. The petroleum cargo, which may notbe evenly distributed especially when the ship is in a ballastcondition, imposes local loads on certain parts of the hull structuresuch as the longitudinal and transverse bulkhead platings, the motion ofthe ship at sea causing inertial forces to be exerted upon the hull.

In the past, tankers have been designed with the object of integratingthe longitudinal bulkhead platings into the main structure of the shipso as to provide added stiifening against the main hull stresses imposedby hogging and sagging while the ship is under way. The liquid cargoexerts hydrostatic stresses (static and dynamic) upon the ships hull sothat these stresses had to be algebraically added to the hogging andsagging stresses in calculating the scantlings for the various membersof the hull structure. The superposition of these stresses on thelongitudinal bulkhead platings frequently resulted in fractures, withthe concomitant dangerous possibility of their spreading to adjoiningstructural elements.

The present invention avoids this superposition of stresses on thelongitudinal bulkheads, these bulkhead platings being so constructedthat they are in effect filling panels and hence need only be designedto withstand the hydrostatic stresses imposed by the liquid cargo.

In accordance with the present invention, the longitudinal bulkheadplatings are composed of sections positioned between reinforced keelsonsat the ships bottom and reinforced continuous girders at the top side,the sections of the, bulkhead being interposed between cruciform strutsarranged as pillaring members in the region of the trans verse bulkheadplatings. In the preferred form of the invention, the longitudinalbulkhead platings are formed from flanged plates in U-form so as to havevertical corrugations. The resulting fluted form of the bulkhead platinghas a taper varying linearly from the bottom to the top in accordancewith the moment of inertia of horizontal sections thereof, adjusted tothe stresses of the liquid cargo.

The new construction reduces the possibility of frac- 2,741,208 PatentedApr. 10, 1956 istic of prior art designs. Also, it facilitatesprefabrica tion and repair, thus lowering both the initial shipbuildingcosts and the costs of maintenance while the tanker is in service.

A better understanding of the invention may be had from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

Fig. l is a reinforced transverse half section in accordance with theinvention, taken along the line 1--1 of a longitudinal bulkhead platingshown in Fig. 3, the port and starboard half sections being identical.

Fig. 2 is an ordinary transverse half section in accordance with theinvention, taken along the line 22 of a longitudinal bulkhead platingshown in Fig. 3, the port and starboard half sections being identical.

Fig. 3 is a horizontal section in accordance with the instant inventiontaken on a reduced scale along the line 33 of a longitudinal bulkheadplating shown in Fig. 1.

Fig. 4 is a horizontal section, also on a reduced scale, of anotherembodiment of a longitudinal bulkhead plating.

Fig. 5 is a perspective view of a longitudinal bulkhead plating inaccordance with the instant invention.

Fig. 6 is a diagrammatic horizontal sectional view, on a reduced scale,as seen from about the level of the line 33 in Fig. 1.

Referring to the drawings, the tanker comprises two longitudinalbulkhead platings 25 (Figs. 1 and 2), running fore and aft and dividingthe cargo portion of the ship into three sections. A number oftransverse bulkhead platings 26 (Fig. 3), placed perpendicular to thelongitudinal bulkhead platings, subdivide these longitudinal sectionsinto tanks, the outboard tanks being called wing tanks (one on the portand one on the starboard side), and the inner tank being called a centertank. Between successive transverse bulkhead platings, the ships hullcomprises reinforced and ordinary sections, as shown in Figs. 1 and 2,respectively. 1

Referring now to Fig. 1, there is shown a reinforced section of a tankerin accordance with the invention. The hull is bounded by a bottom 1,deck 2 and shell 3. In order to help stiflen the ships girder againstfore and aft deflection, longitudinals 4, 5 are provided at the bottomand at the deck, respectively. Under the deck 2, a continuous decktransverse 6 is arranged, and similarly at the bottom 1 a continuousbottom transverse 7 is positioned in the port to starboard direction. Areinforced frame 8 is mounted between the deck and bottom transverses 6,7. Added strength is provided for the hull structure by diagonal ties 9,10. Diagonal tie 9 is secured between lugs 11 and 12, which areintegrated with the reinforced frame 8 and the deck transverse 6,respectively. Similarly, diagonal tie 10 is mounted between lugs 13 and14 integrated with the reinforced frame 8 and the bottom transverse 7,respectively. At the outboard ends of the diagonal ties 9 and 10,stiffeners 15 are secured to the frame 8 and shell 3, while at theinboard ends, stifi'eners 16 and 17 are fastened, respectively, to decktransverse 6 and bottom transverse 7.

Under the deck 2 and on the ships center line is a continuouslongitudinal center line girder, shown generally at 18. The verticalcenter keelson 19, running fore and aft, is positioned on the centerline at the bottom of the hull, and is reinforced by a bracket 21 and aflat plate 20.

Near each side of the ship, a side keelson 22 is provided as addedlongitudinal stiffening for the bottom 1. Each side keelson 22 isreinforced by a fiat plate 23. Under the deck and in vertical alignmentwith each side keelson 22, a continuous girder 24 is similarly pro Isuccessive transverse bulkhead platings.

I deck, girders 24 being reinforced by plates 24a.

As previously stated, the two longitudinal bulk-head platings25partition the-ships breadth into three sections or row's,,eachbulkheadplating. 25 being erected between the reinforced sidekeelson-22atthe bottom and the continuousreinforced girder 24-atthe top. Inaccordance with .the invention, the 1 longitudinal bulkhead plating's 25are formed by means of flanged plates in U -form so as to have verticalcorrugations, as. shown in Figs 3, 4 and 5, The flangedaplatesmaybe-placed butt to butt as in Fig. 3 or overlapped asinFig- 7 Thecorrugated bulkheadplatingsli aretapered, varying linearly from thebottom'at plate 23- to the top under plate 24a. Thisisbest-illustratedin the perspective view shown in Fig. iwhere it willbe t-observed that dimension c at the foot is greaterthanthe-length-btshown at the top.

The longitudinal; bulkhead plating 25 is not. continuous bUtIQ'mlHaIESjust short otja transverse bulkhead plat-' ing26 (Figs. 3eand 4) so asto form sections 25; between terminations of the corrugated bulkheadplatings 25 on each. side of the transverse bulkhead plating 26,cruciform struts 27 extend vertically sojasrtovform a strong pillaringmember between the deck and bottom portions of the ship. As shown in thedrawings, particularly Figs. 3, 4 and6,

these strutsl'l form theintersections-of the longitudinal bulkheadplating 25f. and'thietransverse bulkhead plating 26, the struts'havingarms 21a: secured tothese bulkhead platings in substantiallyliquid-tight relation; to complete the liquid cargo tanks. 7 V

Reterring now, to theftransverse section illustratedwin Fig. 2, thissection comprisesside stringers 29- extending 'foreandaftalongthesideeofythehullg the stringers 29 having brackets 31:. Betweenthe'deckandtop stringer,

a-stiffening'plate 30 is mounted; The bottom longitudinals 4 are securedby'transverse stifiener 32. The vertical center keelsonBis-:strengthenedin this section by, a

r vertical stiffener; The girder24 and side keelson 22 are reinforced bybrackets 3-5; and 33, respectively.

Whenasbip is underway atsea, the hull girder is. subjected tobendingstresses imposed by the;conditions of hogging and sagging.Theterms-hogging and sagg-"are used to refer to-, the twoopposedconditions of longitudinal deflection ot the, ships girder. In thesagging condition, the dfiflfiCtiOH'iiSdGWHWflId,iILthfi region;

: ot midship, while in-theih'ogging condition the d flection isupwardin, this region; Various combinations of hog and. sag can'and do;ofzcourse, occur nder dynamic condi- .tions at sea.

In prior artgdesigns, the longitudinal bulkheadplat ngs areintegratedinto'themainstructure of the ship. so that 7 they cooperate in resis ig. thebending moments imposed by hog andsag; In a-tanker,theelongitudinal bulkhead platings are also; subjected to the static-anddynamic hydrostatic stressesofitheliquidcargo, the motion of the" ship,under way causing, inertial forces to beexerted; Thus; there resultsasuperposition of, the main hull, stresses-(bending 1110111611155 due to:hogging and sagging), and the local. stresses (hydrostaticstressesflacombina tion which is the causeofi'a large number of fractures in theships structure, The;rnostseriousconsequence; of these fractures is. thedanger'offthein spreadingto par Qfthe adjoining structures especiallywhere the ship is of welded construction as is the case in most,moderntankers.

I have found it adyantageousto avoid this superposition of the mainhull; and localstresses. According to my'in girder in resistingthe mainhull stresses, Theglongitudi- Between the 4 nal bulkhead platings 25thus act as filling panels between the above-described members and henceare only required to sustain the local stresses. Accordingly thesebulkhead platings may be designed with scantlings having a reducedmargin sufiicient only to support the hydrostatic loads due to theliquid cargo, thus efiectingvaluable save ings in the weight of theship;

Another advantage of the invention over the prior structures stems fromthe tapered fluted form of the bulkhead plating 25 (Fig. 5). Thisconfiguration enables one to adjust the moment of inertiaof'difierenthorizontal sec tions of the bulkhead plating to the stressestransmitted by the liquid cargo, so that further savings in weight canbe obtained. 7 V

The new construction also facilitates prefabrication and 'makes cleaningandmaintenance in service mucheasier.

The flanged plates for the corrugated longitudinal bulkhead platings 25;maybe lowered into the hold, so: that construction of the main ship.structure can proceed in: dependently. Similarly, when repairs arerequired in the longitudinal bulkhead plating, sections of it mayberemoved. with a, minimum oi'disturbance to the remaining ship-isstructure. I claim:

1. In a tanker'shzp having a shelhbottom and deck,

the combination; of. center. keelson extending longitudibelow: andsecured insubstantially liquid-tight relation to the side keelsonsanddeck girders, said longitudinal bulkhead plating terminatingshort'of thetransverse bulkhead plating, and cmciform struts forming theintersectionsof the bulkhead. plating and extending vertically from theside-keelsons to the deck girders and secured. to'said. side keelsonsand deck: girders and having arms securedto saidlongitudinaliandtransverse bulkhead. plating, all'in substantiallyliquid-tight relation, the bulkhead plating forming with the struts aseries of liquid cargo tanks, the strutsconstituting the main pillaringfor the deck girders, thereby enablingthe use of bulkhead platingofrreduced scantlingc I 2. Thecombination according to claim 1, in whichthe longitudinal bulkhead platings' are corrugated vertically.

3.' The combination according. to claim 1, in which the longitudinalbulkhead platin gs are corrugated vertically, thecorrugations having:greater depth at the-bottom of the bulkheadplatings than at thetopthereof.

4.. The combination according to claim 1, comprising also deck andbot'tonr transverses, a reinforced frame mounted between saidtransverses adjacent the shell, and diagonal ties extending fromsaid'frame to the'deck andbottomtransvers'es', respectively, said tiesterminating adjacent' thevertical' extremities of thelongitudinal'bulk-e 7 head platings.

I References iCited in'the'fileof this patent UNITEDSTATES PATENTS

